Airbag covering cap comprising a support layer and a cover layer of different elasticities

ABSTRACT

An airbag covering cap including a support layer and a covering layer of different elasticities, having at least one tear-off line along which the airbag covering cap tears open when the airbag is deployed. The covering layer is weakened by a groove in the region of the tear-off line and the support layer extends into this groove. The covering layer has a section adjacent to the section of the support layer, which extends into said support layer. The edge between the sections of the support and covering layers, each extending into the other layer is configured as a tear-off edge.

BACKGROUND OF THE INVENTION

The invention relates to an airbag covering cap comprising a supportlayer and cover layer of different elasticities.

From DE 195 16 230 an airbag cover is known which consists of a moldedpart as the support layer and a visible covering which covers the moldedpart to form the cover layer. The cover layer is formed as a leathercoating with a groove-like partial reduction in the material thicknessinto which the support layer is stretched. At this point an ideal breakpoint is formed in the support layer and the path of the break pointcorresponds to that of the groove of the cover layer, i.e., the idealbreak points in the support and cover layer overlap one another.

Through rear injection of the cover layer, molded into the groove, ithappens that there is no material reduction which can be seen on thevisible side of the sight cover and a smooth surface is produced on thevisible side of the cover layer. Ornamental grooves, such as areprovided in the event of weakening the upper side of the cover layer aretherefore not required.

With this covering, as with other known coverings having weakened lines,it is intended that the cover tears open along the weakened lines in theevent of a crash. Tearing open should however not continue over the endof the weakened lines. The drawback with the known covering describedabove is that further tearing beyond the end of the groove cannot beruled out.

In order to prevent further tearing it is known to provide a smallopening at the end of the groove whereby the opening-has a largerdiameter than the width of the break line. This however has the drawbackthat the surface of the cover is broken so that the appearance isimpaired.

Furthermore it is known from DE 44 24 6586 A1 to design the end sectionsof the break line curved so that further tearing beyond the end of thebreak line is likewise to be prevented.

All the known covering caps have the drawback that the opening andtearing force cannot be changed without changing the optical and/ormechanical properties of the covering cap. If the groove is indented forexample to reduce the tear-open force, then the risk of further tearingat the ends is increased.

SUMMARY OF THE INVENTION

The object of the invention is to, in the case of an airbag covering caphaving a smooth cover surface layer, allow the cap to tear open at alower force without the cap continuing to tear further over the end ofthe proposed break line, and to change the opening and further tearingforce without changing the optical and/or mechanical properties.

The airbag covering cap of the present invention includes a support anda cover layer of different elasticity with at least a tear-off linealong which the airbag covering cap tears open as the airbag isdeployed, wherein the cover layer is weakened in the area of thetear-off line through groove and the support layer extends into thisgroove, and wherein the cover layer has, adjoining the section of thesupport layer which extends into the groove, a section which extendsinto the support layer, whereby the edge between the sections of thecover layer and support layer each extend into the other layer, forminga tear-off edge.

As opposed to the known airbag covers, both the support layer and thecover layer have a reinforced section in the area of the break point.Between these two sections stretches a tear-off edge running throughboth layers, i.e., this tear-off edge is, seen in cross-section,substantially longer than with the known covering caps. The coveringcap, in the event of a crash, tears open along this tear-off edgestarting from the weakened lines above the groove in the cover layer,whereby the adhesion between the material of the support and the coverlayer is slight along the tear-off edge. The reinforced sections and theextended tear-off edge on the one hand prevent the airbag covering capfrom tearing open further at the end of the groove of the cover layerand on the other hand ensures in addition that the airbag covering captears open along the proposed line.

In one embodiment, the support layer is designed weaker in the area ofthe tear-off edge between the sections of the support and coveringlayers compared to the remaining areas and the cover layer extends intothe weakened area. With this embodiment both the cover layer and thesupport layer are formed continuous in the area of the tear-off edge.The airbag cover tears open in the event of a crash both at the weakenedpoints of the cover layer and of the support layer and along thetear-off edge between the two layers.

In a further embodiment, it is proposed that the support layer has inthe area of the tear-off edge between the sections of the support andcover layers at least one slit and that the cover layer extends at leastpartially into the slit. With this embodiment the support layer isformed non-continuous in the area of the tear-off edge. Thus with thisembodiment in the event of a crash the airbag cover must only tear in atthe weakened point of the cover layer. It then tears open again alongthe tear-off edge between the support and cover layer.

In a third embodiment, a slit is likewise provided which is howeverbridged by thin narrow webs. The webs preferably have a width of 0.8 mmmaximum and are arranged at intervals of at least 10 mm.

The thickness of the cover layer above the section of the support layerextending into the cover layer preferably increases towards the ends ofthe tear-off areas whereby further tearing of the cover cap can beaffected.

In a further design of the second embodiment, it is proposed that theedge of the slit in the support layer is reinforced like a bead. Areinforcement of this kind is likewise possible with the firstembodiment at the edges of the weakened area in the support layer. It isthereby further ensured that the airbag cover does not tear open apartfrom the proposed tear-open areas.

It is expedient if the tear-off edge runs inclined relative to thesurface of the cover layer and the support layer in this area. Bychanging the inclined path and the path of the tear-off edge incross-section it is possible to adjust the initial tearing and furthertearing forces without changing the optical or mechanical properties.The tear-off edge preferably runs straight in cross-section but can alsorun angled in a straight line or curved.

The reduced adhesion provided between the support and cover layer at thetear-off edge can be achieved by selecting suitable materials for thesupport and cover layer whereby the adhesion is also reduced in theremaining areas. The reduced adhesion can also be achieved by surfacetreating the support layer in this area prior to applying the coverlayer.

It is expedient to use thermoplastics elastomers as the support layerand cover layer.

The invention will now be explained with reference to the embodimentsshown in the drawings in which:

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of the underneath of a covering cap;

FIG. 2 is a sectional view through the covering cap along line A—A ofFIG. 1;

FIGS. 3-6 show different embodiments of the tear-off area of thecovering cap in an enlarged view of the detail marked by a circle inFIG. 2;

FIG. 7 shows a view from below of the detail of FIG. 6 with a continuousweb;

FIG. 8 shows a view from below of the detail of FIG. 6 with severalnarrow webs.

DETAILED DESCRIPTION OF THE INVENTION

The covering cap 1, shown in FIG. 1, tears open into two parts in theevent of a crash. To this end two folding areas 2, 3 are provided whichhave in the center of the covering cap a common tear-off area 4. At theends there are separate tear-off areas 5, 6 and 7, 8 which open intohinge-like sections 9, 10 which are designed, in a known way, forexample, as film hinges and are not shown in detail.

It can be seen from FIG. 2 that the covering cap has a support layer 11with an edge 12 and that a cover layer 13 is provided over the supportlayer 11. Both preferably consist of plastic whereby the material of thecover layer is softer than the material of the support layer. The coverlayer 13 has a continuous surface while it is designed on the underneathin the manner according to the invention.

In a first embodiment which is shown on an enlarged scale in FIG. 3, thecover layer has in the tear-off areas 4-8, a groove into which a section11 a of the support layer extends. The support layer has in the tear-offareas 4-8, a slit, i.e., the folding areas 2, 3 are separated from eachother in the support layer. A section 13 a of the cover layer 13 extendsinto this slit. A tear-off edge 14 runs between the two sections 11 aand 13 a. In the present embodiment, this tear-off edge runs in astraight line in cross-section and extends practically through theentire support and cover layers. The support and cover layers receiveincreased strength in the area of this tear-off edge 14 through thereinforced sections 11 a and 13 a so that further tearing at the ends ofthe tear-off areas 5-8 which adjoin the hinge-like sections 9, 10 isprevented. Furthermore by changing the incline of the tear-off edge 14it is possible to affect the force required for initially tearing andfurther tearing the cover cap without changing the optical andmechanical properties of the tear-off area, i.e., both the continuoussurface of the cover layer 13 and also the reinforced sections 11 a and13 a remain.

The thickness, d, of the cover layer 13 above the section 11 apreferably amounts to a few tenths of a millimeter and at the ends ofthe tear-off areas 5-8 to about one millimeter.

During inflation, the support layer 11 and the cover layer 13 expanddifferently as a result of unequal elasticity. The cover material tearsin over the reinforced section 11 a of the support layer 11 and becomesdetached from the support material along the inclined tear-off edge 14.The adhesion between the support and cover layers is, however, so greaton the other side that the two layers remain joined together duringtearing of the covering cap in the remaining areas so that the coveringcap tears open completely.

With the embodiment of FIG. 4 there is a different path for the tear-offedge compared with the embodiment of FIG. 3. In cross-section thistear-off edge 15 runs straight with angles, i.e., it has two sectionswhich run at different angles relative to the surface of the coveringcap.

A modification of the embodiment of FIG. 4 is shown in FIG. 5. There thesupport layer has in the area of the tear-off edge 15 bead-likereinforcements 16, 17.

The process of the further tearing along the tear-off edge 15 is therebyfurther improved.

In FIG. 6, the two embodiments of FIGS. 7 and 8 are shown incross-section. With the embodiment of FIG. 7 the support layer 11 has noslit in the area of the tear-off edge but a weakening in the material sothat a web 18 remains. In the present embodiment the weakening has beenprovided on both sides. The weakened section 13 a of the cover layer 13extends into the weakened area of the support layer up to the web 18.The web has such a width that despite the different elasticities of thesupport and cover layer it tears open together with the cover layerabove the reinforced section 11 a.

In the embodiment of FIG. 8 the support layer 11 has a slit which isbridged by webs 19 which extend from one side of the support layer 11 tothe other side. The reinforced section 13 a can thus be seen in FIG. 8between the webs 19.

What is claimed:
 1. An airbag covering cap comprising: a support layerand a cover layer of different elasticities, wherein the support has atleast one tear line, wherein the cover layer has a groove forming aweakened area along the tear line, wherein the support layer has asupport layer section that extends into the groove, wherein the coverlayer has a cover layer section that extends into the support layer,adjacent to the support layer section, and along the tear line, whereinan edge formed between the support layer section and the cover layersection forms the tear line, and wherein the support layer has at leastone slit along the tear line and wherein the cover layer section extendsat least in part into the at least one slit, and further including aplurality of thin narrow webs bridging the slit.
 2. An airbag coveringcap according to claim 1, wherein the webs have a width of 0.8 mmmaximum and are arranged at intervals of at least 10 mm.
 3. An airbagcovering cap a support layer and a cover layer of differentelasticities, wherein the support has at least one tear line, whereinthe cover layer has a groove forming a weakened area along the tearline, wherein the support layer has a support layer section that extendsinto the groove, wherein the cover layer has a cover layer section thatextends into the support layer, adjacent to the support layer section,and along the tear line, wherein an edge formed between the supportlayer section and the cover layer section forms the tear line, whereinthe support layer has at least one slit along the tear line and whereinthe cover layer section extends at least in part into the at least oneslit, and wherein the support layer includes bead-like reinforcements onan edge of the at least one slit.
 4. An airbag covering cap comprising:a support layer and a cover layer of different elasticities, wherein thesupport has at least one tear line, wherein the cover layer has a grooveforming a weakened area along the tear line, wherein the support layerhas a support layer section that extends into the groove, wherein thecover layer has a cover layer section that extends into the supportlayer, adjacent to the support layer section, and along the tear line,wherein an edge formed between the support layer section and the coverlayer section forms the tear line, wherein the support layer is weakeralong the tear line than the remaining area thereof, and wherein thesupport and cover layers have reduced adhesion at the tear line.
 5. Anairbag covering cap according to claim 4, wherein the support layer hasa plurality of tear lines, each having ends where the thickness (d) ofthe cover layer section, above the support layer section extends intothe cover layer, increases.
 6. An airbag covering cap according to claim4, wherein the tear line is inclined along opposite surfaces of thecover layer section and support layer section.
 7. An airbag covering capaccording to claim 4, wherein the tear line, viewed in cross-section,runs in one of a straight line, angled in straight lines, or curved. 8.An airbag covering cap according to claim 4, wherein the support andcover layers comprise thermoplastic elastomers.
 9. An airbag coveringcap according to claim 4, wherein said support layer is formed with anopen slit which extends along the tear line from an inboard surfacetoward the cover layer and which renders the support layer weaker alongthe tear line.
 10. An air bag covering cap according to claim 9, furthercomprising a thin narrow web which bridges and closes the open slit. 11.An air bag covering cap comprising: a support layer and a cover layer ofdifferent elasticities, wherein the support has at least one tear line,wherein the cover layer has a groove forming a weakened area along thetear line, wherein the support layer has a support layer section thatextends into the groove, wherein the cover layer has a cover layersection that extends into the support layer, adjacent to the supportlayer section, and along the tear line, wherein an edge formed betweenthe support layer section and the cover layer section forms the tearline, wherein the support layer is weaker along the tear line than theremaining area thereof, and wherein the materials selected for thesupport and cover layers have mutually reduced adhesion.
 12. An airbagcovering cap comprising: a support layer and a cover layer of differentelasticities, wherein the support has at least one tear line, whereinthe cover layer has a groove forming a weakened area along the tearline, wherein the support layer has a support layer section that extendsinto the groove, wherein the cover layer has a cover layer section thatextends into the support layer, adjacent to the support layer section,and along the tear line, wherein an edge formed between the supportlayer section and the cover layer section forms the tear line, andwherein the support layer has at least one slit along the tear line andwherein the cover layer section extends at least in part into the atleast one slit wherein the slit is a through slit which extends alongthe tear line and wherein the cover layer section extends at least inpart into the at least one slit, and further comprising: a thin narrowweb which bridges and closes the slit.